Personally, for sendings and what not?
I wouldn't send Jelanda until you at least get Yumei and/or Nanami. You ALWAYS want at least one mage in your team, and Jelanda's your only one for a little while (Nanami and Yumei can join as early as Chapter 2, and as late as Chapter 4, I wanna say?)
For sendings, you just need to fulfill as many reqs as Freya asks for that chapter. If you can get one character who fulfills all the requirements, then you only need to send one. You also do NOT need to fulfill all of Freya's requirements to get the majority of the benefits (probably just affects Materialize Points; getting the good gear just requires you fulfill a majority of them.) Sending 2 characters up isn't a bad idea, of course, if you have characters to spare and don't plan on using them.
In Chap 1, send just one of Llewellyn or Belenus. The only requirement is, IIRC, Hero Value, which you'll get if you max out their Personality traits, and that should get you the full benefits Freya gives you. And if it doesn't...Chap 1-2 sacred phase rewards are pretty meager anyway <_<